There is no DSL repository. When you re-enable apt it will download packages from the Debian repositories. The default is to use oldstable (woody). If you want you can change the sources.list to point to stable (sarge) or even testing/unstable.

The majority of the time you'll have no problems installing from debs. However as DSL is not pure Debian (there are a number of additions which are not debian packages) you might may very ocassionally run into conflicts/issues.